NASHVILLE, Tenn. -- The Nationals seem to be betting that Dan Haren's down year resulted from a two-month slump, rather than the beginning of a decline phase.

If they're right, they got quite a bargain on Tuesday. Haren, 32, agreed to a one-year deal with the reigning National League East champs, joining a rotation that already included Stephen Strasburg, Gio Gonzalez and Jordan Zimmermann. Haren battled back troubles en route to the worst season of his Major League career, but the shape of his 2012 season suggests there may be a lot left in the tank.

Over the season's first two months, Haren was his usual self. He struck out nearly a batter per inning, posted a strikeout-to-walk ratio in the high 4s and churned out 6 1/2 innings per start. Over his final nine starts, it was a similar story -- 43 K's against eight walks and a 3.48 ERA, though under six innings per start.

In between, Haren battled a back injury and scuffled to a 6.24 ERA over 10 miserable midseason starts. If it's as simple as he was compromised in June and July but all right by mid-August, look out for the Nats in '13.

"I think it's great," said manager Davey Johnson during Day 2 of the Winter Meetings on Tuesday. "I've got some young guys that act like veterans, and they pitched like veterans last year for me, and a veteran like Dan Haren is just going to make things even better. I think he's a great addition. I've seen him pitch a lot over the years, intense competitor, and hopefully we'll get that done."

From a contract perspective, it's hard not to like the deal. Washington committed only one year to a player who likely would have commanded an enormous deal if he'd hit the market one year earlier. As the saying goes, there's almost no such thing as a bad one-year contract.

The move finishes out the Nationals' rotation, with Haren joining the three aces listed above as well as developing young lefty Ross Detwiler. He's the second significant addition by a team that has chosen to be bold rather than resting on its laurels following a Major League-best 98-win season. The Nats deserve credit for that aggression; the desire to bring back a winning team intact often leads to mistakes.

And they're almost certainly not done with the remodeling. In addition to adding Haren and Denard Span, the Nationals are likely to make at least one more move. They'd like to bring back first baseman Adam LaRoche, which would allow them to trade first baseman/outfielder Michael Morse.

However, that raises another question: what for? The Nats are in sufficiently strong position that if they sign LaRoche, they actually don't have to deal Morse. There's no obvious weakness to be shored up. They could add starting-pitching depth or relief help. Or they could package Morse with another player for a bigger upgrade somewhere.